1. Field of the Invention
The present invention relates to a terminal apparatus, a positioning method, a control program for the terminal apparatus, and a computer readable recording medium having recorded therein the control program for the terminal apparatus.
2. Background Information
Conventionally, a positioning system that locates a present position of a SPS receiver using, for example, a SPS (Satellite Positioning System), which is a satellite navigation system using positioning satellites, has been used. This SPS receiver is constituted to detect a signal frequency (a reception signal frequency) from a signal received from a SPS satellite based on orbit information of the SPS satellite stored in advance. The SPS receiver then synchronizes itself with the reception signal frequency by a synchronizer provided in the SPS receiver to thereby receive the signal from the SPS satellite.
However, the frequency of a crystal oscillator, which is an example of the synchronizer of the SPS receiver, fluctuates depending on the temperature. Thus, the SPS receiver cannot be synchronized with the reception signal frequency in a consistent manner, it takes a longer time to position the SPS receiver.
To cope with this problem, there has been proposed a technique in which information indicating a fluctuation in the frequency of the SPS receiver that was observed last time the positioning was performed, and when a signal is to be received from the SPS satellite next time, the SPS receiver synchronizes itself with the reception signal frequency taking into account the fluctuation of the frequency of the last time. Japanese Patent Application Publication 5-256926 (FIG. 1, etc.) discloses an example of such construction.
However, in such conventional arrangement, there is a problem that, for example, when the temperature changes since the last time the positioning was performed, the amount of fluctuation of the frequency also changes significantly. Accordingly, the synchronization cannot be performed promptly, and long time is required for positioning of the SPS satellite.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved terminal apparatus, a positioning method, a control program for the terminal apparatus, and a computer readable recording medium having recorded therein the control program for the terminal apparatus that overcome the problems of the conventional art. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.